Tail the animal had got caught in (6)
I believe the answer is:
shadow
'tail' is the definition.
('shadow' can be a synonym of 'tail')
'the animal had got caught in' is the wordplay.
'the animal' becomes 'sow'.
'had got' becomes 'had' ('have' can be a synonym of 'have got').
'caught in' indicates putting letters inside.
'sow' placed around 'had' is 'SHADOW'.
(Other definitions for shadow that I've seen before include "Secretly tail someone" , "Sort of boxer - dog" , "Ghost" , "Trail" , "Opposer" .)